(See Tim's LEGO Reviews for my reviews of past LEGO Minifigures series.)
Due to the COVID-19 pandemic, I never did acquire any of the Series 20 Minifigures, but I did recently visit a local store that had the Series 21 figures. Fortunately, the character I wanted most, the Centaur Warrior, is very easy to find by feel thanks to her large horse body piece. I was able to find several of them within just a few minutes, and then spent some more time looking for the others I wanted.
I now own 7 of the 12 characters in this series. (Note that it's a smaller series that most, with only a dozen characters instead of the usual 16.) I did not buy the Airplane Girl, Beekeeper, Pug Costume Guy, Space Police Guy, and Violin Kid, so am omitting them from my mini-reviews below. Rest assured, however, that if you're looking for Airplane Girl, the big wings of her costume are almost as easy to find by feel as the centaur body. The Beekeeper's hat and square tile honeycomb are very distinct as well, as is the Space Police's shield and armor. (Is it just me, or does issuing a policeman with a riot shield and baton seems rather tone-deaf to major news stories of the past year or two? If I acquire more of this series, I'll be skipping that one.)
Alien: This alien wears an orange bodysuit and carries a crowbar and a crystal that it likely just extracted from a mine. Its species is unclear due to a mask covering part of its face. The mottled skin and small spines on the back of the head suggest reptilian or amphibian, or even insectoid or more bizarre. (My wife will be using this minifigure for her shirren, an insectoid race in the Starfinder RPG.)
Ancient Warrior: This warrior is based on an Aztec Jaguar Warrior, with a feathered feline headdress, a shield with stylized jaguar face, and even jaguar-print tattoos or bodypaint, and clawed toes. The head is double-sided: one smiling, and one snarling with fangs. He wields a macuahuitl, a flat wooden club edged with sharpened pieces of obsidian. (This weapon is the main reason I wanted this character, because a recent session of the Grey Angels campaign involved stealing magical ones from an auction.)
Cabaret Singer: This performer wears a glittery teal and purple costume with a silver fabric train and a feathered headdress, with matching makeup on a double-sided head--one face smiling, the other with eyes closed as she belts out her song. She comes with a microphone and stand, which uses a 1x1 round plate with a hole in the stud as the base, so it can be mounted on a baseplate's stud.
Centaur Warrior: This character's body is the same piece as the centaurs from Forbidden Forest: Umbridge's Encounter*, but in caramel and brown. The body is a bit smaller than a standard LEGO horse--about half an inch shorter both vertically and horizontally--but I think this smaller size looks more in scale with the minifigure. It's also easier to fit this centaur into a Large (2") space than a horse, and not horrible outsized for the playable centaur race in D&D 5E, which is technically Medium-sized.
The torso has a sleeveless green garment, with a tree motif, and the wrists have matching bracers. She has a bow, and a quiver that can be hung from one of the studs in her back. She also comes with an apple--but whether that's supposed to indicate her forest home, or be used as a target (ala William Tell) is unclear.
(*The centaurs and the giant in the Umbridge's Encounter set are very appealing, but J.K. Rowling's very public transphobic comments over the past year or two have made my family resolve to not buy any more tie-in products to her creations. So I was very pleased to see the centaur body re-released as part of the Minifigures line.)
Ladybug Girl: This woman wears a spotted black and red ladybug costume, including a helmet with antennae, and a short, split cape like the insect's wings. Her head is double-sided, with two different smiles. She comes with a leaf and a 1x1 round tile printed to look like a ladybug. As with most parts this small, my bag came with an extra tile, which could be handy for anyone wanting more tiny vermin.
This minifigure makes a serviceable Medium-sized beetle as-is by bending her over onto all fours.
Paddle Surfer: This woman is clearly fond of dolphins: she has one printed on her wetsuit (though her life vest covers it) and she has found one to paddle near. Her head is double-sided, one side having sunglasses, and her ballcap is combined with hair in a ponytail.
The dolphin is the same as used in the Friends theme, in a neutral gray. There are "anti-studs" on the bottom side of the flukes, so that the dolphin can be stood up on its tail on the baseplate, as if leaping out of the water. Strangely, the bottom surface between the flippers is exactly the same as the bottom of a minifigure torso, so it's possible to create a weird mutant dolphin-monster with human legs. It looks ridiculous--and a bit creepy.
Shipwreck Survivor: This castaway wears tattered pants and a seashell necklace, and has an anchor tattoo. The head is printed with a beard, which is fully covered by the hair piece's shaggy mop. He also comes with a bottle printed to look like it has a rolled-up message inside.
He is accompanied by a tiny, cute hermit crab. The shell, made of a 1x1 round plate (with a hole on the stud) and a cupcake (or ice cream?) piece, is attached to a small post on the back of the crab's body. Stacking multiple 1x1 round plates on this post allows other things to be attached to the crab--such as a tail to turn it into a scorpion.
Or, on a more silly note, make it into the tiniest reality show contestant ever!